This invention relates to a transparent touch panel, which may be attached on display devices such as liquid crystal display panel enabling an operator to input by a pressure with finger or pen while viewing what is displayed on the panel.
There have been various types of panels proposed as the transparent touch panel to be used with electronic apparatus or other equipment; such as the resistance layer type, electro static capacitance type, sensor type, etc.
A standard model of transparent touch panel is described below, referring to drawing. FIG. 1 shows a cross sectional view of the essential part of a standard transparent touch panel. In FIG. 1, base plate 1 is a 0.1-3 mm thick substrate made of glass or a transparent high polymer, for example, polyethylene terephthalate, polycarbonate, polyacrylate, etc. Top plate 2 is a 0.1-0.5 mm thick substrate made of glass or a transparent high polymer, for example, polyethylene terephthalate, polycarbonate, polyacrylate, etc. On the inner surface of the base plate 1 is a transparent electro conductive layer 3, and on the inner surface of the top plate 2 is a transparent electro conductive layer 4; positioned with the electro conductive layer 3 and the electro conductive layer 4 facing to each other. Dot spacers 5 are placed between the base plate 1 and the top plate 2 with a certain interval there between in order to provide a clearance between the base plate 1 and the top plate 2. The base plate 1 and the top plate 2 are fixed by means of adhesive body 6 made up of an adhesive of epoxy resin or acrylic resin, or a tack agent of polyvinyl alcohol, polyacrylate, etc.
With the above mentioned constitution, the operation of standard transparent touch panel is explained herewith. When the upper surface of top plate 2 is pressed with a finger or a pen, the dot spacer 5 deforms allowing the transparent electro conductive layer 4 placed underneath the top plate 2 to touch the transparent electro conductive layer 3 located on the upper surface of the base plate 1, and an electric signal is obtained.
Now, in the following, a conventional transparent touch panel is described. In the constitution of a transparent touch panel as shown in FIG. 1, conventional dot spacers employed a soft silicone rubber material in order to enable the top plate 2 work with a soft touching.
However, the conventional transparent touch panel comprising dot spacers made of a soft silicone rubber material has a problem in durability over a long time of service; namely, during the operating life, the dot spacer itself deteriorates significantly and easily peels off from the plate.